Resist collapse prevention using immersed hardening

ABSTRACT

A method, tool, and machine for hardening a photoresist image while the photoresist image is immersed in a liquid.

FIELD OF THE INVENTION

This invention relates to methods of making semiconductor devices, andmore particularly, to a method of making a semiconductor deviceincluding forming a photoresist features and treating the same toprevent the photoresist features from collapsing.

BACKGROUND OF THE INVENTION

FIG. 1 illustrates a prior art method of making a semiconductor deviceincluding providing a semiconductor device 10 with a first layer 6 suchas a dielectric layer having an upper surface 8. A photoresist layer 26is deposited over the upper surface 8 of the first layer 6 and patternedand a development composition 22 is flowed over the photoresist layer 26so that individual photoresist features are defined, such as a firstphotoresist feature 12 and a second photoresist feature 14 with a gap 16therebetween. The first photoresist feature 12 includes an inside wall18 facing an inside wall 20 of the second photoresist feature 14. Thephotoresist features 12 and 14 have an outside wall 19 and 21respectively. FIG. 2 illustrates a prior art step in the semiconductormanufacturing wherein the development fluid or rinse fluid is spun dryin an effort to leave the individual photoresist features 12, 14.However, the photoresist features 12, 14 can collapse as illustrated inFIG. 2. The collapsing becomes more prevalent in situations where theaspect ratio, that is the photoresist thickness (height)/photoresistwidth ratio is greater than 3. The collapse problem is also prevalentwhen small photoresist features such as line widths less than 150 nm areformed.

As will be appreciated from FIG. 2, when the photoresist collapsestypically the inner side wall 18 of the first photoresist feature 12engages the inner side wall 20 of the second photoresist feature 14 toclose off the gap 16 that was therebetween. FIG. 4 is a planillustration of the collapsed photoresist features 12 and 14. It will beappreciated that there is no opening or gap 16 between the firstphotoresist feature 12 and the second photoresist feature 14 andtherefore wet or dry etching materials, or other material cannot passbetween the photoresist features.

Messick et al., U.S. Pat. No. 6,451,510, discloses one solution topreventing photoresist collapse. Messick et al. discloses a method ofdeveloping photoresist patterns on electronic component substrates suchas semiconductor wafers using specially defined developer compositionsin sequence with a specially defined rinse composition to develop anexposed photoresist pattern and then the developed pattern is rinsed.Both the developer composition and the rinse composition contain ananionic surfactant and, when these solutions are used in sequence, theyform a photoresist pattern which avoids pattern collapse even with smallfeatures such as line widths less than 150 nm and with aspect ratiosgreater than about 3. Disclosed as suitable anionic surfactants areammonium perfluoroalkyl sulfonate and ammonium perfluoroalkylcarboxylate.

The present invention provides alternatives to the prior art.

SUMMARY OF THE INVENTION

One embodiment of the invention includes a method of making asemiconductor device including immersing a photoresist image in a liquidand hardening the photoresist image while immersed in the liquid.

In one embodiment of the invention the hardening of the photoresistimage comprises directing infrared light on a photoresist image.

In another embodiment of the invention the hardening of the photoresistimage comprises directing infrared radiation comprising wavelengthsranging from 700 nm to 2 micrometers.

One embodiment of the invention further comprises heating the liquidprior to immersing the photoresist image therein.

One embodiment of the invention further comprises pressurizing theliquid to raise its boiling point.

In another embodiment of the invention the liquid comprises a reactivesubstance to react with the photoresist.

In one embodiment of the invention the hardening comprises electricallyheating of the liquid.

In another embodiment of the invention the liquid comprises water andfurther comprising electrically heating the water.

In another embodiment of the invention the hardening comprises directingultraviolet light on the photoresist image.

In another embodiment of the invention comprises directing ultravioletlight on the photoresist image and heating the liquid.

Another embodiment of the invention comprises directing ultravioletlight on the photoresist image and wherein the ultraviolet lightincludes wavelengths between 150 nm and 480 nm.

In another embodiment of the invention the liquid comprises asurfactant.

In another embodiment of the invention the surfactant comprises analcohol.

In another embodiment of the invention the photoresist comprises amaterial including at least one of OH⁻ or COO⁻ functional groups andwherein the liquid comprises a chemical that reacts with at least of onesaid functional groups.

Another embodiment of the invention comprises a tool for hardening aphotoresist image while the photoresist image is immersed in a liquid.

Another embodiment of the invention further includes a pressurizingmeans for the liquid.

Another embodiment of the invention includes a heating means for theliquid.

Another embodiment of the invention includes an ultraviolet illuminator.

Another embodiment of the invention includes an ultraviolet illuminatorcomprising at least one ultraviolet source and at least one ultravioletcondenser.

Another embodiment of the invention includes an ultraviolet light sourcecapable of producing wavelengths between 150 nm and 480 nm.

Another embodiment of the invention comprises an infrared illuminator.

Another embodiment of the invention comprises an infrared illuminatorcomprising at least one infrared source and at least one infraredcondenser.

Another embodiment of the invention includes an infrared light sourcecapable of producing wavelengths between 700 nm and 2 micrometers.

Another embodiment of the invention includes a chamber and means forflowing a liquid into the chamber.

Another embodiment of the invention includes a semiconductor waferassembly machine comprising a photoresist depositing station, anexposure station, a PEB station, a developing station, a rinse station,a photoresist hardening station, and a drying station.

Other embodiments of the present invention will become apparent from thedetailed description provided hereinafter. It should be understood thatthe detailed description and specific examples, while indicating thepreferred embodiment of the invention, are intended for purposes ofillustration only and are not intended to limit the scope of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will become more fully understoodfrom the detailed description and the accompanying drawings, wherein:

FIG. 1 illustrates a prior art method of developing a photoresist image.

FIG. 2 illustrates a prior art method wherein photoresist featurescollapse during spin drying.

FIG. 3 illustrates the capillary force in the fluid between photoresistelements.

FIG. 4 illustrates a plan view of a prior art semiconductor withphotoresist elements collapsed.

FIG. 5A illustrates a method according to one embodiment of the presentinvention including forming a photoresist layer over a substrate.

FIG. 5B illustrates a method according to one embodiment of the presentinvention including exposing the photoresist layer.

FIG. 5C illustrates a method according to one embodiment of the presentinvention including a PEB step.

FIG. 5D illustrates a method according to one embodiment of the presentinvention including immersing a photoresist layer in a developercomposition.

FIG. 5E illustrates a method according to one embodiment of the presentinvention including rinsing the photoresist layer.

FIG. 5F illustrates a method according to one embodiment of the presentinvention including directing ultraviolet light onto the photoresistimage while the image is immersed in a fluid to harden the photoresistimage.

FIG. 5G illustrates a method according to one embodiment of the presentinvention including spin drying the semiconductor device after thephotoresist image has been hardened and so that the photoresist imagefeatures do not collapse.

FIG. 6 illustrates an alternative embodiment of the present inventionincluding heating a liquid in which a photoresist image is immersed toharden the photoresist image.

FIG. 7 illustrates a semiconductor manufacturing tool according to oneembodiment of the present invention.

FIG. 8 illustrates a semiconductor assembly machine according to oneembodiment of the present invention including a variety of stations.

FIG. 9 illustrates a plan view of a semiconductor wafer according to oneembodiment of the present invention including photoresist image that hasbeen hardened while immersed in a fluid according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

Referring now to FIG. 3, as indicated earlier, a semiconductor device 10may include a first photoresist feature 12 and a second photoresistfeature 14 with a gap 16 therebetween. The first photoresist element 12includes an inner wall 18 which is hydrophilic. The second photoresistelement 14 includes an inner wall 20 which is also hydrophilic. Oneaspect of the present invention includes the discovery that the adjacentphotoresist elements 12 and 14 create a capillary force in the fluid 22that is therebetween.

Referring now to FIGS. 5A-G, one embodiment of the present inventionincludes making a semiconductor device including depositing aphotoresist layer 26 over a first layer 24, which may be a substrate,dielectric layer, or metallization layer as shown in FIG. 5A. As shownin FIG. 5B, the photoresist layer 26 is exposed to light 28 shownthrough a mask 31 including blocking portions 33 that do not allow lightto pass therethrough. The photoresist layer 26 includes exposed portions25 and unexposed portions 27. As shown in FIG. 5C, the photoresist layer26 is then subjected to a post exposure bake (PEB) step.

Thereafter, the photoresist layer 26 is exposed to a developercomposition 32 which dissolves the exposed portion 25 of the photoresistlayer 26 as shown in FIG. 5D. Referring now to FIG. 5E, thesemiconductor device is rinsed so that the remaining unexposed portions27 of the photoresist layer 26 are immersed in the rinse solution 34. Asshown in FIG. 5F, thereafter the photoresist image is hardened, forexample, by exposing the remaining elements 27 to ultraviolet light 106while the photoresist elements 27 are immersed in a liquid 34. As shownin FIG. 5G, the semiconductor device 10 is then dried, for example, byspin drying to remove the rinse liquid and so that the photoresistelements 12 and 14 do not collapse and a gap 16 remains therebetween.

Referring now to FIG. 6, an alternative embodiment of the presentinvention includes heating the liquid 34 in which the photoresistelements 27 are immersed. The heating of the liquid 34 may occur priorto immersing the photoresist elements 27 in the liquid 34 or after thephotoresist elements 27 have been immersed in the liquid 34, forexample, by using a heater 108. The heating of the liquid may beaccomplished by electrical heating, liquid gas heat exchanger or anyother method known to those skilled in the art of heating a liquid. Theliquid may be placed under pressure by, for example, by charging a gasthrough a port 110 into the chamber 42.

Referring now to FIG. 7, one embodiment of the invention includes a toolfor hardening a photoresist image while immersed in the liquid. The tool40 may include a chamber 42 and a support 44 for a semiconductor wafer.The tool may include an illuminator 46 which may be, for example, anultraviolet light illuminator or an infrared radiation illuminator. Thetool may also include a means for heating 38 a fluid introduced into thechamber, for example, through a port 100. The tool 40 may also include ameans for applying pressure to the fluid, for example by, charging gasthrough a gas port 48.

Referring now to FIG. 8, one embodiment of the invention includes asemiconductor machine including a photoresist depositing station 50, anexposure station 52 for exposing the photoresist material deposited onthe semiconductor wafer, a PEB station 54, a developing station 56, arinsing station 58, a photoresist hardening station 60 and a dryingstation 70.

In conventional processing, dense photoresist patterns suffer fromcollapse. To prevent such collapse, prior methods kept the photoresistthickness/width ratio to less than 3. However, conventional etchingprocesses often require this ratio to be greater than 3. The problem waseven worse for ArF photoresist because ArF photoresist is less etchresistant. Furthermore, design features for ArF photoresist are smallerthan KrF photoresist. The hardening method of the present inventionovercomes these prior art problems and the method can be used to makephotoresist features in dense design dimensions and using a variety ofexposure sources without the photoresist collapsing during the dryingstep. The photoresist features hardened according to the presentinvention allow for the trimming of the photoresist features to reducethe width of the feature. The photoresist features may be trimmer usinga laser after the drying step.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A method of making a semiconductor device comprising: forming aphotoresist image on a semiconductor device; immersing the photoresistimage in a liquid bath; pressurizing said liquid bath while saidphotoresist image is immersed in said liquid bath; hardening thephotoresist image while immersed in the pressurized liquid bath; and,drying the photoresist image.
 2. A method as set forth in claim 1wherein the hardening comprises exposing the photoresist image toinfrared light.
 3. A method as set forth in claim 1 wherein thehardening comprises exposing the photoresist image to infrared radiationcomprising wavelengths ranging from 700 nm to 2 micrometers.
 4. A methodas set forth in claim 1 wherein the hardening comprises heating theliquid.
 5. A method as set forth in claim 4 further comprising asubstance in the liquid to react with the photoresist.
 6. A method asset forth in claim 1 wherein the hardening comprises heating the liquidwith electrical heating.
 7. A method as set forth in claim 1 wherein thehardening comprises heating the semiconductor wafer.
 8. A method as setforth in claim 1 wherein the hardening comprises exposing thephotoresist image to ultraviolet light.
 9. A method as set forth inclaim 8 wherein the liquid is heated.
 10. A method as set forth in claim8 wherein the ultraviolet light comprises wavelengths ranging from 150nm to 480 nm.
 11. A method as set forth in claim 1 wherein the liquidcomprises water.
 12. A method as set forth in claim 1 wherein the liquidcomprises water and a surfactant.
 13. A method as set forth in claim 1wherein the liquid comprises a surfactant.
 14. A method as set forth inclaim 13 wherein the surfactant comprises an alcohol.
 15. A method asset forth in claim 1 wherein the liquid comprises a chemical that reactswith the photoresist image.
 16. A method as set forth in claim 1 whereinthe photoresist image includes at least one of OH⁻ and COO⁻ functionalgroups, and wherein the liquid includes a chemical that reacts with atleast one of said functional groups.
 17. A method as set forth in claim1 wherein the hardening comprises exposing the photoresist image toultraviolet light, and wherein the liquid includes a surfactant.
 18. Amethod as set forth in claim 1 wherein the forming of the photoresistimage comprises selectively exposing a photoresist layer to lightgenerated from an ArF source.
 19. A method as set forth in claim 1wherein the forming of the photoresist image comprises selectivelyexposing a photoresist layer to light generated from an KrF source. 20.A method as set forth in claim 1 wherein the photoresist image includesphotoresist features having an aspect ratio greater than
 3. 21. A methodas set forth in claim 1 wherein the photoresist image includesphotoresist features having a width less than 150 nm.
 22. A method asset forth in claim 1 wherein the photoresist image includes a pluralityof individual features, and further comprising trimming the individualfeature to reduce the width of the same following said step of hardeningthe photoresist image.
 23. A method of making a semiconductor devicecomprising: forming a photoresist image on a semiconductor device, saidphotoresist image including at least one of OH⁻ and COO⁻ functionalgroups; immersing the photoresist image in a liquid bath, wherein theliquid bath is pressurized and the liquid includes a chemical other thana surfactant that reacts with at least one of said functional groups;hardening the photoresist image while immersed in the liquid; and,drying the photoresist image.
 24. A method as set forth in claim 23wherein the hardening comprises exposing the photoresist image toinfrared light.
 25. A method as set forth in claim 23 wherein thehardening comprises heating the liquid.
 26. A method as set forth inclaim 23 wherein the hardening comprises heating the liquid withelectrical heating.
 27. A method as set forth in claim 23 wherein thehardening comprises heating the semiconductor water.
 28. A method as setforth in claim 23 wherein the hardening comprises exposing thephotoresist image to ultraviolet light.
 29. A method as set forth inclaim 23 wherein the liquid comprises water.
 30. A method as set forthin claim 23 wherein the liquid comprises a surfactant.
 31. A method asset forth in claim 30 wherein the surfactant comprises an alcohol.
 32. Amethod as set forth in claim 23 wherein the photoresist image includes aplurality of individual features, and further comprising trimming theindividual feature to reduce the width of the same following said stepof hardening the photoresist image.
 33. A method as set forth in claim32, wherein said trimming is performed using a laser.
 34. A method asset forth in claim 22, wherein said trimming is performed using a laser.35. A method of making a semiconductor device comprising: forming aphotoresist image on a semiconductor device; immersing the photoresistimage in a liquid bath; pressurizing said liquid bath while saidphotoresist image is immersed in said liquid bath; hardening thephotoresist image while immersed in the pressurized liquid bath; dryingthe photoresist image; and, trimming features comprising saidphotoresist image to reduce a width of said features.
 36. A method asset forth in claim 35, wherein said trimming is performed using a laser.37. A method as set forth in claim 35, wherein said hardening isselected from the group consisting of heating said photoresist image andexposing said photoresist image to ultraviolet light.
 38. A method asset forth in claim 35, wherein the photoresist image includes at leastone of OH⁻ and COO⁻ functional groups, and wherein the liquid includes achemical that reacts with at least one of said functional groups.